In designing machinery for the processing of substrates and individual IC units, key factors such as minimizing waste, maintaining units per hour (UPH) and limiting downtime for retooling are all key design determinants.
Considering adaptability of said machines, in order for a machine to be useful for a range of applications, it will be necessary for it to accommodate substrates having different spacing between the IC units. Whilst the machine can be retooled for each application, it would be more efficient if the machine can be adapted relatively simply to accommodate said spacing. In particular the picker assemblies used to transport the singulated IC units between stations are dependent upon the spacing of the units in order to engage the units collectively. It would therefore be useful if the spacing of the pickers within the picker assembly could be adjusted to accommodate substrates having different IC unit spacing.
Some systems have been trialled to achieve this function. For instance, one system uses a threaded rod to connect each of the pickers within an assembly. In this case, the thread is at discreet location to coincide with the position of each picker. Further, the thread for each pair of pickers symmetrically placed around a centre line varying based on position, such that rotation of the threaded rod will move the outer pickers further than the inner pickers. Accordingly, the pitch of each portion of the thread will vary based upon the distance from the centre line, and further, with the thread on one side being a forward thread and a reverse thread on the corresponding other side of the centre line.
Whilst this is a simple and direct solution, the manufacture of such a rod may be extremely time consuming and therefore extremely expensive. Any detritus, such as grit, on one of the thread portions may cause damage to the thread, which may require the entire rod to be replaced. Given the environment in which the picker assembly operates, material from a sawing process may be caught in the mechanism. Consequently, the lifetime cost of such a picker assembly based upon replacement of the threaded rod may be considerable.
It would be beneficial if the system for varying the spacing of pickers were both simple in operation and relatively inexpensive also.
In another consideration, with decreasing profit margins for integrated circuits, and in particular, memory, the pressure to reduce processing costs is significant and hence the need to speed production whilst maintaining quality. It follows that the cost of infrastructure to achieve these processes will equally suffer from pressure to reduce cost whilst maintaining speed and quality.
Given the volume of integrated circuit chips contained within a substrate, a potential bottleneck is the ability for the various systems to move the IC units from station to station once singulated. Different systems have been developed to achieve this, for instance that disclosed in PCT/SG2005/000288, the contents of which are incorporated herein by reference. In order for the unit pickers to engage individual IC units, the unit picker assembly involves a complex arrangement designed to engage the various units in a specified manner. Whilst both efficient and effective, the cost and maintenance of such equipment may be particularly high.
Further, such systems are known to create a degree of friction, as well as the potential for backlash.
It would therefore be advantageous to adopt a unit picker assembly that incorporates aspects that may lead to a lower capital cost.